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Welcome to the 3500HD.com forum created October 2009

Author Topic: load sensing proportioning valve?  (Read 2157 times)

jim in n.y.

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load sensing proportioning valve?
« on: July 24, 2016, 09:20:11 PM »
I know the older Chevy 3/4 and 1 ton trucks came with a rear load sensing proportioning valve to be able to apply more braking power based on the load. How come the 3500HD's don't have one? Is the braking power controlled by the ABS? If so and there was no ABS or non functioning ABS ( no computer) should a load sensing prop valve be used from maybe an older K3500? Thoughts?
                         Jim

                 
'84 chevy stepside , Detroit 3-53T w/Jakes, spicer 3853-B 5 spd. with O/D. 3.08's
'88 K5 Blazer ,350 TBI ,700R4,3.73's soon to be 6.2L Turbo
'84 crew cab dually 2wd ,350,SM465 w/4.10's
'97 3500HD was 6.5L w/4L80 & 4.63's hope to have 6V-53T w/Allison 2000

Raymo

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  • Location: Port Huron Area, MI
Re: load sensing proportioning valve?
« Reply #1 on: July 25, 2016, 04:18:40 PM »
Both my '94 and '91 HD's had them. I have the one from my '91 but the valve itself it's junk.
'94 3500-HD, Cummins, Getrag, NP205. Shortend rear frame with a Pickup Bed. Dana 60 front, stock 80 rear.

'03 2500-HD 8.1 and Allison

jim in n.y.

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  • Location: wilton n.y.
Re: load sensing proportioning valve?
« Reply #2 on: July 26, 2016, 04:01:32 AM »
Thanks for the reply.
    Lots of things have been robbed off my '97 but the brake lines near the rear diff. don't seemed to have been touched . Looks all factory. Nice bends no kinks . I wonder if all years had them. Just trying to figure out if I need to scrounge one up.
'84 chevy stepside , Detroit 3-53T w/Jakes, spicer 3853-B 5 spd. with O/D. 3.08's
'88 K5 Blazer ,350 TBI ,700R4,3.73's soon to be 6.2L Turbo
'84 crew cab dually 2wd ,350,SM465 w/4.10's
'97 3500HD was 6.5L w/4L80 & 4.63's hope to have 6V-53T w/Allison 2000

ED-NY

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  • Location: Champlain, NY
Re: load sensing proportioning valve?
« Reply #3 on: July 26, 2016, 09:03:37 AM »
I'm not really up on these valves but would think they were intended for very heavy & tall load truck beds like dump beds etc?  Maybe a normal duty flatbed would do fine without one???

someotherguy

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Re: load sensing proportioning valve?
« Reply #4 on: July 26, 2016, 09:33:08 AM »
My '94 had one.  My '95 didn't, but the hard line going to the bracket for the flex hose looks like it may not have been original, looking back on my old pics.

Can't remember if the '93 did, or if the '98 company truck I drove had one.

Richard
06 Silverado ISS / 06 Silverado SS / 06 300C SRT8

jim in n.y.

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  • Location: wilton n.y.
Re: load sensing proportioning valve?
« Reply #5 on: July 26, 2016, 09:31:22 PM »
Thanks for the replies guys.
    Something seems strange about this truck. There is also no evidence of it having rear anti-lock brakes. I was under the impression they had 4 wheel ABS. No wires going down the frame and no wires at the wheels for the ABS sensors either. Didn't they have ABS by '97?  I'll have to check the front wheels.
'84 chevy stepside , Detroit 3-53T w/Jakes, spicer 3853-B 5 spd. with O/D. 3.08's
'88 K5 Blazer ,350 TBI ,700R4,3.73's soon to be 6.2L Turbo
'84 crew cab dually 2wd ,350,SM465 w/4.10's
'97 3500HD was 6.5L w/4L80 & 4.63's hope to have 6V-53T w/Allison 2000

someotherguy

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Re: load sensing proportioning valve?
« Reply #6 on: July 27, 2016, 09:57:30 AM »
I've never studied the 4WAL system on the 1995-up GMT4xx trucks very closely but I am fairly certain there are no rear wheel sensors; they take that signal from the vehicle speed sensor (VSS)

Richard
06 Silverado ISS / 06 Silverado SS / 06 300C SRT8

240g

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Re: load sensing proportioning valve?
« Reply #7 on: July 27, 2016, 10:35:03 PM »
My 93 has the valve, my 96 does not. I'm pretty sure it never did, as all appears factory back there and there is no evidence of the bracket ever being bolted there.

jim in n.y.

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Re: load sensing proportioning valve?
« Reply #8 on: July 29, 2016, 06:48:11 AM »
Ok,
   My '97 does in fact have the front wheel ABS wires and sensors. So, apparently it is just front wheel ABS  and not 4 wheel. As far as the load sensing prop. valve goes I guess it must have been an option? Maybe part of a brake system or suspension  package. I've looked at a lot of trucks lately and some have it and some don't. No cronology to it like the frame stiffening plate.
        Jim
'84 chevy stepside , Detroit 3-53T w/Jakes, spicer 3853-B 5 spd. with O/D. 3.08's
'88 K5 Blazer ,350 TBI ,700R4,3.73's soon to be 6.2L Turbo
'84 crew cab dually 2wd ,350,SM465 w/4.10's
'97 3500HD was 6.5L w/4L80 & 4.63's hope to have 6V-53T w/Allison 2000

someotherguy

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Re: load sensing proportioning valve?
« Reply #9 on: July 29, 2016, 10:17:59 AM »
From 1995-up, it's 4 wheel ABS.  There just aren't any sensors on the rear wheels, as I said earlier.

Richard
06 Silverado ISS / 06 Silverado SS / 06 300C SRT8

jim in n.y.

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  • Location: wilton n.y.
Re: load sensing proportioning valve?
« Reply #10 on: July 29, 2016, 09:21:25 PM »
Someotherguy,
   Re-read your post and now I see what you meant about rear wheels  taking from the VSS. Sorry for the confusion.
         Jim
'84 chevy stepside , Detroit 3-53T w/Jakes, spicer 3853-B 5 spd. with O/D. 3.08's
'88 K5 Blazer ,350 TBI ,700R4,3.73's soon to be 6.2L Turbo
'84 crew cab dually 2wd ,350,SM465 w/4.10's
'97 3500HD was 6.5L w/4L80 & 4.63's hope to have 6V-53T w/Allison 2000

 


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